1. Field of the Invention
The present invention relates to an aluminum alloy engine block for an internal combustion engine, the block incorporating tubular cylinder liners made from a material or an alloy that is different from the composition of the aluminum alloy engine block. More particularly, the present invention relates to an aluminum alloy engine block into which cylindrical liners are adapted to be physically pressed, in which the liners are formed from either a ferrous alloy or an aluminum alloy, and in which the interfaces between the outer surfaces of the liners and the inner surface of the respective cylinder bores are metallurgically bonded to provide a firm interconnection and good heat transfer.
2. Description of the Related Art
Engine blocks for internal combustion engines, such as those engines adapted to be installed in vehicles, such as automobiles, have for a long time been made of cast iron for the necessary rigidity, and also for resistance to cylinder wear caused by the rapid sliding movement within a cylinder bore of a cylindrical piston having several piston rings. The use of cast iron results in a very heavy engine which, because of its weight, requires increased fuel consumption to operate the automobile, which runs counter to the modern trend of providing lighter weight automobiles and lighter weight engines for increased fuel economy.
One way to provide a lighter engine is to make the engine block from an aluminum alloy that has the required strength and wear attributes, because aluminum alloys have a considerably lower density which results in lighter weight. Although aluminum alloys are available that are suitable for casting and that have the required resistance to wear to ensure long, trouble-free engine life, at times it might be desirable to provide an engine block formed from one aluminum alloy and a cylinder liner that is formed from a second aluminum alloy. Additionally, there are times when it might be desirable to provide cylinder liners that are made of cast iron. In that regard, U.S. Pat. No. 4,637,110, which issued on Jan. 20, 1987, to Hiroshi Yamagata, discloses an aluminum alloy engine block for a two-cycle engine. A cast iron cylinder liner is cut from a section of cylindrical pipe, and lateral port openings are formed in the liner, which is subsequently pressed into the cylinder bore provided in the engine block. However the mere mechanical connection between a cylinder liner and a cylinder bore is discontinuous and often inadequate to provide an unimpeded heat transfer path over the physical interface between the liner and the cylinder bore.
Another description of the insertion of a cylinder liner into a light weight cast aluminum alloy engine block appears in U.S. Pat. No. 4,986,230, which issued on Jan. 22, 1991, to James R. Panyard et al. The latter patent teaches a method for mechanically bonding a cylinder liner to a cylinder bore by inserting the liner into the bore and then forcing a mandrel through the interior of the liner to stretch the liner radially outwardly against the inner surface of the cylinder bore to provide increased surface-to-surface contact area. However because of the process disclosed, the liner must be made from a ductile material, which normally rules out cast iron, and consequently requires the liner be made of a high-ductility steel having at least 30% elongation capability. Again, because of the mechanical bond between the liner and the bore, uniform and unimpeded heat transfer is difficult to maintain.
It is an object of the present invention to overcome the deficiencies in the prior art arrangements for securing a cylinder liner in a bore in an aluminum alloy engine block.
It is another object of the present invention to provide an aluminum alloy engine block having cylinder liners that are made of materials different from that of the block and in which the liner and block are joined by a metallurgical bond.